This invention relates to an RF coil (radio frequency coil), to a magnetic resonance signal measuring apparatus and to a magnetic resonance imaging apparatus. In particular, it relates to an RF coil in proximity to and surrounding an imaging subject, to a magnetic resonance signal measuring apparatus using this RF coil, and to a magnetic resonance imaging apparatus using this magnetic resonance signal measuring apparatus.
In a magnetic resonance imaging apparatus, an RF coil is disposed in proximity to an imaging subject, and a magnetic resonance signal is measured at a position as close as possible to an imaging site so as to improve the SNR (signal-to-noise ratio) of the signal.
The RF coil used for imaging the head has a substantially cylindrical shape and accommodates the whole of the head in the internal space of a cylinder. However, if the nose is not to come in contact with the wall, the coil diameter will be too large compared to the effective diameter of the head, and a high SNR will not necessarily be obtained.
It is therefore object of this invention to provide an RF coil which can effectively image a head, a magnetic resonance signal measuring apparatus using this RF coil, and a magnetic resonance imaging apparatus using this community resonance signal measuring apparatus.
(1) The invention from one aspect to resolve the above problem is an RF coil comprising a plurality of first coil loops having a substantially cylindrical shape and coaxially disposed from one end side to a center part in the axial direction of a space housing an imaging subject, a plurality of second coil loops having a part projecting in a direction effectively perpendicular to the axial direction and coaxially disposed from another end side to the center part, and a supporting frame supporting the first and second coil loops in one piece, whereof at least the other end side in the axial direction is open.
The invention from this aspect uses a combination of two types of coil loop, i.e., a coil loop which has a projecting part in one direction and a coil loop which does not. Consequently, the RF coil fits the forehead and nose which have different diameters, and can accommodate them.
(2) The invention from another aspect to resolve the above problem is an RF coil wherein the first and second coil loops are formed using a rod-shaped conductor whereof parts arranged in the aforesaid direction are not covered by the supporting frame except the parts at the two ends in the axial direction.
In the invention from this aspect, the coil loop part cutting across the face of the imaging subject is a rod-shaped conductor, and as the width per unit cross-section is small, the openness in front of the face is increased.
(3) The invention from another aspect to resolve the above problems is an RF coil as defined in (2), wherein the rod-shaped conductor comprises a transparent coating.
In the invention from this aspect, the coating of the rod-shaped conductor is transparent, so obstruction of the visual field due to the thickness of the coating is reduced. Further, more outside light enters and the interior is bright.
(4) The invention from another aspect to resolve the above problems is an RF coil as defined in any of (1) to (3), wherein the supporting frame comprises an opening in a direction effectively perpendicular to the axial direction and the aforesaid direction.
In the invention from this aspect, the supporting frame is open also in the lateral direction, so openness is high. Further, the permeability to air is improved.
(5) The invention from another aspect to resolve the above problems is an RF coil as defined in any of (1) to (4), wherein a reflecting mirror is attached to the supporting frame.
In the invention from this aspect, a visual field in a predetermined direction is maintained by bending the line of site by the reflecting mirror.
(6) The invention from another aspect to resolve the above problems is an RF coil as defined in (5), wherein the position of the reflecting mirror can be varied in the axial direction.
In the invention from this aspect, the position of the reflecting the mirror is variable, so adaptation to individual differences in imaging subjects can therefore be made.
(7) The invention from another aspect to resolve the above problems is a magnetic resonance signal measuring apparatus, comprising a plurality of first coil loops having a substantially cylindrical shape and coaxially disposed from one end side to a center part in the axial direction of a space housing an imaging subject, a plurality of second coil loops having a part projecting in a direction effectively perpendicular to the axial direction and coaxially disposed from another end side to the center part, a supporting frame supporting the first and second coil loops in one piece, whereof at least the other end side in the axial direction is open, and a magnetic resonance signal measuring means connected to these coil loops.
In the invention from this aspect, a combination of two types of coil loop, i.e., a coil loop which has a projecting part in one direction and a coil loop which does not, is used. Consequently, the RF coil fits the forehead and nose which have different diameters, and can accommodate them. A magnetic resonance signal can be measured with a high SNR by this RF coil.
(8) The invention from another aspect to resolve the above problems is a magnetic resonance imaging apparatus, comprising a static magnetic field forming means which forms a static magnetic field in a space housing an imaging subject, a gradient magnetic field forming means which forms a gradient magnetic field in the space, a high frequency magnetic field forming means which forms a high frequency magnetic field in the space, a plurality of first coil loops having a substantially cylindrical shape and coaxially disposed from one end side to a center part in the axial direction of a space housing an imaging subject, a plurality of second coil loops having a part projecting in a direction effectively perpendicular to the axial direction and coaxially disposed from another end side to the center part, a supporting frame supporting the first and second coil loops in one piece, whereof at least the other end side in the axial direction is open, a magnetic resonance signal measuring means connected to these coil loops, and an image-generating means which generates an image based on the magnetic resonance signal measured by the magnetic resonance signal measuring means.
In the invention from this aspect, a combination of two types of coil loop, i.e., a coil loop which has a projecting part in one direction and a coil loop which does not, is used. Consequently, the RF coil fits the forehead and nose which have different diameters, and can accommodate them. A magnetic resonance signal can be measured with a high SNR by this RF coil, and a high-quality image can be generated based on the measured signal.
According to this invention, an RF coil, magnetic resonance signal measuring apparatus using this RF coil, and magnetic resonance imaging apparatus using this magnetic resonance signal measuring apparatus can be provided.
Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings.